Air barrier systems control movement of air, and specifically water vapor, across a surface of a structure, such as a building enclosure. In exterior walls, uncontrolled air flow is the greatest source of moisture and condensation damage. Indoor comfort is affected by air temperature, relative humidity, direction of airflow and surrounding surface temperatures. Indoor air quality is enhanced by air barrier systems by efficiently keeping pollutants out of building interiors. Pollutants include water vapor, suspended particulates, dust, insects, smells, etc. Air barrier systems have significant impact on electricity consumption and gas bills. Air barrier systems in nonresidential buildings are estimated to reduce air leakage by up to 83 percent, reduce gas bills more than 40% and reduce electricity consumption more than 25% according to simulations by the National Institute of Standards and Technology (NIST) compared to typical buildings without air barriers. Water vapor is a key ingredient in corrosion and mold growth. Air barrier systems help prevent water vapor from being transported by air movement between exteriors and interiors of structures, such as buildings.
The use of air barrier systems has been a requirement in Canada for almost 25 years and is becoming important in North America due to net zero energy requirements by 2030, required by the US Army Corp of Engineering, ASHRAE 90, and International Energy Conservation Code—2009. On Dec. 16, 2011, the DC Construction Codes Coordinating Board (CCCB) adopted the 2012 International Energy Conservation Code (IECC).
Previously known waterproofing sheets having both waterproofing property and moisture permeability have been developed. One typical example of such moisture-permeable waterproofing sheets is flash-spun nonwoven fabrics. U.S. Pat. No. 3,169,899, for example, discloses a flash-spun nonwoven fabric. U.S. Pat. No. 3,532,589 discloses a method for producing a flash-spun nonwoven fabric. The nonwoven fabric thus obtained has an appropriate pore size. It blocks water, but allows water vapor to pass therethrough. A known example of the nonwoven fabric is commercially available under the trade designation “Tyvek” from E. I. Du Pont de Nemours and Company, Wilmington, Del. USA obtained by thermo-compressing a three-dimensionally-meshed fiber of high-density polyethylene. Such a moisture-permeable waterproofing sheet can prevent external water from infiltrating through the sheet, but can drain gathered moisture as water vapor.
However, the openings such as windows or doors are not flat. It is difficult to form a waterproofing layer only with a waterproofing sheet, and therefore the opening is often finished with a waterproofing tape with a pressure sensitive adhesive layer provided thereon. In this case, since the pressure sensitive adhesive layer is made of rubber or asphalt materials, the moisture vapor permeability of the entire tape decreases, and the same problem as that of a common waterproofing sheet can occur.
Mechanical fasteners or adhesive fasteners, such as pressure sensitive adhesive tapes, can be used to affix the moisture-vapor permeable waterproofing sheet on substrates of exterior walls or to affix overlapped portions of two moisture-vapor permeable waterproofing sheets. As a result, moisture may permeate from gaps of such fasteners, such as nail holes, over a long period of time. It is beneficial for such moisture-vapor permeable waterproofing sheets to pass ASTM D-1970/D-1970M-13 or similar modified tests such as Modified Test 1 of ASTM D-1970/D-1970M-13, Modified Test 2 of ASTM D-1970/D-1970M-13, or Modified Test 3 of ASTM D-1970/D-1970M-13 for nail sealability. It is also beneficial to provide easy application of the air and water barrier article to substrates, such as building components. Because self-adhered air barrier articles are used in wide width format, they can be difficult to handle. Application of air barrier articles is simplified if the release liner comes off on the external face of the air barrier article. This allows for removal of the liner after the air barrier article has been applied to a surface rather than simultaneously removing the liner while the air barrier article is being applied or removing the liner before application of the air barrier article.
It is also beneficial for the adhesives provided on the air barrier articles to provide robust adhesion in a variety of conditions. For example, it is beneficial for such an adhesive to adhere to wet substrates, which are common conditions on surfaces of building components at a construction site.